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package main
import (
"bufio"
"fmt"
"os"
"strings"
)
func main() {
fmt.Println(part1(readData("example.txt")))
fmt.Println(part1(readData("data.txt")))
fmt.Println(part2(readData("example2.txt")))
fmt.Println(part2(readData("data.txt")))
}
func readData(fileName string) (output []string) {
fp, err := os.Open(fileName)
if err != nil {
panic(err)
}
scanner := bufio.NewScanner(fp)
output = make([]string, 0)
for scanner.Scan() {
output = append(output, strings.TrimSpace(scanner.Text()))
}
return
}
func part1(s []string) (count int) {
width := len(s[0])
height := len(s)
for y := 0; y < height; y++ {
for x := 0; x < width; x++ {
if s[y][x] == 'X' {
count += checkXmas0(s, x, y)
}
}
}
return
}
func checkXmas0(s []string, x, y int) (count int) {
count += checkXmas1(s, x, y, 0)
if x >= 3 {
count += checkXmas1(s, x, y, -1)
}
if x < len(s[0])-3 {
count += checkXmas1(s, x, y, 1)
}
return
}
func checkXmas1(s []string, x, y, dx int) (count int) {
count += checkXmas2(s, x, y, dx, 0)
if y >= 3 {
count += checkXmas2(s, x, y, dx, -1)
}
if y < len(s)-3 {
count += checkXmas2(s, x, y, dx, 1)
}
return
}
const WORD string = "XMAS"
func checkXmas2(s []string, x, y, dx, dy int) int {
if dx == 0 && dy == 0 {
return 0
}
for i := 0; i < 4; i++ {
if s[y][x] != WORD[i] {
return 0
}
x += dx
y += dy
}
return 1
}
func part2(s []string) (count int) {
width := len(s[0])
height := len(s)
str := []byte{0, 0, 0, 0}
for y := 1; y < height-1; y++ {
for x := 1; x < width-1; x++ {
if s[y][x] == 'A' {
str[0] = s[y-1][x-1]
str[1] = s[y-1][x+1]
str[2] = s[y+1][x+1]
str[3] = s[y+1][x-1]
count += checkXMas(str)
}
}
}
return
}
func checkXMas(b []byte) int {
i := 3
j := 0
for n := 0; n < 4; n++ {
if b[i] == 'S' && b[j] == 'M' {
break
}
i = j
j += 1
}
if b[j%4] == 'M' && b[(j+1)%4] == 'M' && b[(j+2)%4] == 'S' && b[(j+3)%4] == 'S' {
return 1
}
return 0
}
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